Digester with gas lifts positioned by gas-lock tubes



DIGESTER WITH GAS LIFTS POSITIONED BY GAS-LOCK TUBES Filed D80. 19, 1960 J. D. WALKER June 8, 1965 INV EV TOR. ames ,Dom/ flb/Xez' .J. D. WALKER June 8, 1965 DIGESTER WITHGAS ,LIF'I'S POSI'IIONED BY GAS-LOCK TUBES Filed Dec. 19. 1960 2 Sheets-Sheet 2 INVEN TOR 1 w m a M w m W, M4M

United StatesPatent DIGESTER WITH GAS LIFTS PUSITHONED BY GAS-LGCK TUBES James Donald Walker, Aurora, Ill., assignor, by mesne assignments, to Walker Process Equipment, Inc, Wilmington, Del., a corporation of Delaware Filed Dec. 19, 1960, Ser. No. 76,813

Claims. (Cl. 2lil97) Before the present invention, removable gas supply tubes for gas lifts in digesters for sewage sludges, have presented a problem in regard to locating the gas liberat ing orifices, which are at the foot of the tube, at the correc point in the cross section of the updraft tube. V r

Efficiency is reducedif the gas liberation is concentrated toward one side of the updraft tube, especially if the updraft tube is near the maximum diameter that is eificient for the particular gas liberating device. Prior to this invention removable tubes have been centered by fins at or in the vicinity of the gas liberating device. Such fins have a tendency to clog. In an effort to minimize clogging, fins have been foreshortened so that there is a clearance between them and the members that they contacted for centering purposes so that stringy material could slip through and free itself from the vane. Such foreshortening of :the vane reduces the accuracy of their centering function, and unless the accuracy is greatly reduced, clogging still occurs occasionally.

According to the present invention, the vanes within the updraft tube are entirely eliminated, the supply tube being accurately positioned by widely spaced positioning means above the liquid level. Furthermore, these widely spaced positioning means are provided at substantially no extra cost because they utilize a gas-lock seal tube which is provided anyway. At the upper end of the gas-lock tube, the means which must be provided for sealing between the gas-lock tube and the gas supply tube constitutes a positioning means at that point. Spaced well below this, positioning fingers can be secured to the gas supply tube to engage or approximately engage the inside surfaces of the gas-lock tube for accurately positioning this part of the gas supply tube. Being accurately positioned at two widely spaced points, the foot of the. gas

supply tube will likewise be positioned with sufiicient accuracy.

The invention as thus far discussed was first the subject of my earlier application Ser. No. 787,5*l9, filed January 19, 1 959, abandoned after filing of the present application.- The present application is to incorporate with it a more recent improvement, in which the position of the gas liberating device can be adjusted for greater accuracy by adjusting the angle of the gas-lock seal tube. The present application is a continuation-in-part of the aforementioned Serial No. 787,519.

When more than one'gas liberating device is needed (in large installations), lower construction cost is achieved by providing a singlelarge diameter updraft tube. This has not been practical before this invention (in its earlier form), because non-clog fins couldnot position a plurality of gas liberating units. One unit with arms ex tending todifferent areas would also be objectionable because of clogging troubles.

Additional advantages and objects of theinvention wil be apparent from the following description and from the drawings. 7

Designation of figures FIGURE 1 is a somewhat diagrammatic general view of a digester embodying this invention.

FIGURE'Z is a vertical sectional View taken approxi sister! Patented June 8, 1965 ice form of the invention as contemplated, in less detail, in FIG. 1.

FIG. 3 is a horizontal sectional view taken approximately along the line 33 of FIG. 2.

General Description Although the following disclosure offered for public dissemination is detailed to ensure adequacy and aid underst-anding, this is not intended to prejudice that purpose of a patent which is to cover each new inventive concept therein no matter how others may later disguise it by variations in form or additions or further improvements. The claims at the end-hereof are intended as the chief aid toward this purpose, as it -is these that meet the requirement of pointing out the parts, improvements, or combinations in which the inventive concepts are found.

The invention is illustrated in connection with digester it which may be conventional in many respects. It may be provided with a sealed roof lZ desiged to trap gas thereunder above the liquid level of the digesting liquor or sludge. The roof may be fixed or floating, but has been illustrated as fixed. Raw sludge to be treated is supplied through a raw sludge pipe 13. An overflow pipe 14 has been illustrated, the liquor preferably flowing through it from a level below the liquid level, as at 16. Persons skilled in the art Will recognize that there may be several such pipes all open to the atmosphere, with adjustable sleeves, so that the one with the lowest sleeve maintains the liquid in the tank to the level of the top of its sleeve. 'The settled sludge may be drawn off through a pipe 17. Gas which is generated by the digestion process rises to the space under the roof and is drawn off by a pipe 18 for use or storage.

It has been proposed long ago to provide for circulation of the contents of the digester by a gas lift device.

The gas lift device commonly includes an updraft tube such as a tube 21 open at its bottom and top. The top is preferably below the liquid level, for maximum eflicieney. Gas is liberated within the tube through a plurality of gas liberating devices 22, the gas being supplied by a pump 23 having an intake 24 drawing gas from within the space below the roof 12.

best in connection with FIG. 2. It is not practical to use i one gas supply tube and a cross member for liberating gas at widely spaced points, because stringy material would catch on the cross member. A single slim or streamlined gas liberating device at the foot of each gas supply tube is the surest way to avoid clogging by an accumulation of stringy material.

Gas-lock tubes Each supply pipe 31 extends down through a gas-lock tube 32 carried by and sealed to a plate 33 forming a part of the roof 12, or a manhole cover thereon. Tube 32 could be welded to plate 33 and was so shown in the earlier application; Preferably, however, it is secured to plate 33 by being welded to an adjustably mounted flange,

as shown for reasons described below. The tube 32 extends Well below the water level maintained by the overflow device 1-5, or below the minimum water level if the water level is subject to variations. In the illustrated form of the invention the gas-lock tube 32 extends approximately a foot and a half below the water level. The gas supply tube 31 is sealed to the gas-lock tube 32 by a disk or cap plate '34 which is sealed to both. As gas is liberated through orifices 36, perhaps four of which maybe located snares? around the lower portion of gas liberating device 22, some of this gas will initially pass upwardly into the space between gas-lock tube 32 and supply pipe 31. However, cap 34 prevents the escape of this gas and when the interpipe space 37 has been filled with gas, any additional gas will flow outside of gas-lock tube 32 to be trapped below the roof 12.

When it is desired to remove a gas supply tube 31 for inspection or servicing of the orifices 36, a union or slip joint 33 (which may extend out from the side of cap 41, instead of the top asshown) is opened to separate the structure to be removed from a supply connection 39. The cap 41 is then removed by removing bolts 42. This frees the supply pipe 31 so that it may simply be lifted out. Preferably a bail 43 is provided by which the supply ipe 33 may easily be lifted out. The bail 43 may conveniently be welded to disk 34, to which is also welded the supply pipe 31. The Weld of pipe 31 to plate 34 extends all around pipe 31 and seals one with respect to the other. Gaskets 44 seal disk 34 to the flanges on the upperextension of gas-lock tube 32 and on cap 41 respectively.

Accurate positioning of gas supply tube The gas supply tube is accurately centered at a high level by cap 34. It is accurately positioned or centered at a substantially lower level by guide pins or fingers as which may be welded to the outside of the supply pipe 31. Thus the cap plate 34 and the guide fingersde cooperate to accurately position the gas liberation unit 22 in the center of gas-lock tube 32 and with the proper lateral location in updraft tube 21. So as to center the supply pipe 31 with reasonable accuracy but without binding, the ends of guide fingers 46 have slight clearance with gaslock tube 32 and at least three and preferably four guide fingers 46 are provided, spaced uniformly around supply pipe 31.

it has been found in practice that the positioning of the discharge portion 22 of the gas supply tube 31 does not always work out exactly as planned. It is apparent, for example, that if the plate 33 should not be exactly level, or if the gas seal tube 32 should be welded to it at a slight variant from the intended perpendicularity, or if the updraft tube 21 should be slightly misplaced or slightly inclined from the vertical, then the discharge portion 22 of the gas supply tube 31 would be accordingly displaced from its intended position. This is easily remedied, according to a further feature of this invention, which is added by this second application.

Instead of being welded to the plate 33, the gas seal tube 32 is welded to a flange 51. This flange 51 is sealed to the plate 33 by a resiliently compressible gasket 52. The angularity of the flange 51 can be varied slightly with respect to the plate 33 by a set of adjusting screws 53, one

of which is seen in FIG; 2 and the others in FIG. 3. Gasket 52 is of such thickness as to accommodate such adjustment, or it may be located to operate on vertical surfaces with substantially constant thickness. In addition to the adjustment screws 53 there is preferably another set of screws 54 one of which is seen in FIG. 2 and the others in FIG. 3. The screws 54- are secured and sealed to the plate 33 by welding, and provide studs upstanding three and preferably four of the adjustment screws 53 evenly spaced around gas seal tube 32 and an equal number of studs 54 interspersed evenly between the screws 53, as seen in FIG. 3.

This manner of accurately locating the gas liberation 'unit 22 makes it possible to dispense with any centering vanes within the upflow tube 21, and hence there is a minimum opportunity for clogging within the tube 21. it

' alsobecomes entirely practical to use a large cross section Sealing, action Since the pumping of gas through supply pipes 31 is discontinued when they are about to be removed, there will be substantially no gas flowing up into any gas-lock tube 32 while the supply pipes 31 are being withdrawn or while they are out. Of'course, a minute amount of gas generated in the slurry directly below the gas-lock tubes 32 may rise into this tube and escape, but such a small quantity is not excessive either from the standpoint of its value or from the standpoint of a hazard. It would be very objectionable for the main body of gas below the roof 12 to escape. This loss would not only be wasteful but its mixture with air would present a tire hazard. Even aside from explosive or inflammable mixtures, large quantitles of the gas would represent a health hazard to workmen removing the supply pipes. The seal tubes, or gas lock tubes 32 extend deeply enough into the watery liquor of the digester to prevent any escape of the main body of gas.

I claim:

1. A dige'ster including a substantially gas-tight tank having a roof, overflow means for retaining liquor in the tank to a predetermined level, an opening in the roof, plurality of a means to close said opening including gaslock tubes sealed to the roof around said opening and from it. It is apparent that during field installation, the v gas seal tube 32 can be lowered throughthe aperture 56 provided for it until the flange 51 can be fitted over the upstanding threaded studs of bolts 54. Of course, the nuts 57 will have first been removed and the gasket 52 set in place. Before filling the digester, the screws 53 can be adjusted to whatever extent may be necessary to position the dischargeportion 22 of the down draft tube 31 accurately in its intended position. The accuracy can be de'termined'by a sight hole, not shown looking down into the updraft tube 21 or by a worker entering the empty digester, as through a manhole 58. Once the right adjustment is determined, lock nuts 59 are tightened and nuts 57 applied and also'tightened. There should be at least each tube extending down into the tank to a substantial distance below said level to retain gas in the tank in the .space above the liquor when saidtube is open, screw means associated with each gas-lock tube adjacent the roof for adjusting the angularity of the tube in. any direction, and a gas supply pipe extending down through each tube to "a point below the tube, gas liberating means carried by each pipe substantially below the tube, means normally sealing each pipe to its surrounding tube but, said pipe with its gas liberating means, being removable upwardly through the tube and the opening, said pipe being rigidly positioned in the upper part of said gas-lock tube and having means closely positioned with respect to the gas-lock tube at a point substantially lower therein than the point of its rigid positioning, and with its gas liberating means being of substantially rigid nature throughout its length from the point of its rigid positioning down to adjacent the point of gas liberation, whereby the gas liberating'means are accurately positioned with respect to each other, the plurality of gas liberating means being located in proximity to one another to cooperate in producing a'single gas lift column.

2. A dige'stcr including a substantially gas-tight tank having a roof, overflow means for retaining liquor in the tank to a predetermined level, an opening in the roof, means to cl-ose'sa-id opening including a gas-lock tube sealed to the roof around said opening and extending down into the tank to a substantial distance below said I level to retain gas in the tank in the space above the liquor means carried by the pipe below the tube, means normally sealing said pipe to said tube but, said pipe with its gas liberating means, being removable upwardly through the tube and the opening, and an updraft tube surrounding the gas liberating means, and spaced therefrom and from the gas-lock tube; said pipe being rigidly positioned in the upper part of said gas-lock tube and having means closely positioned with respect to the gas-lock tube at a point substantially lower therein than the point of its rigid positioning, and with its gas liberating means being of substantially rigid nature throughout its length from the point of its rigid positioning down to adjacent the point of gas liberation, whereby the gas liberating means are accurately positioned within the updraft tube; said digester including screw means associated with the gas lock tube adjacent the roof for adjusting in any lateral direction the location of the gas liberating means.

3. Equipmet for a digester including a roof member, having an opening therein, means to close said opening including a gas-lock tube sealedto the roof member around said opening and extending a substantial distance below said roof member to extend below the liquid level in the digester to retain gas in the digester in the space above the liquor when said tube is open, a gas supply pipe extending down through the tube to a point below the tube, gas liberating means carried by the pipe below the tube, means normally sealing said pipe to said tube but, said pipe with its gas liberating means, being removable upwardly through the tube and the opening, and an updraft tube surrounding the gas liberating means, and spaced therefrom and from the gas-lock tube; said pipe being rigidly positioned in the upper part of said gas-lock tube and having means closely positioned with respect to the gas-lock tube at a point substantially lower therein than the point "of its rigid positioning, and with its gas liberating means being of substantially rigid nature throughout its length from the point of its rigid positioning down to adjacent the point of gas liberation, whereby the gas liberating means are accurately positioned within the updraft tube; said digester including screw means associated with the gas lock tube adjacent the roof for adjusting in any lateral direction the location of the gas liberating means. a

4. A gas liberating assembly for a liquid-treating tank having a cover provided with an opening, including a closure plate for said opening, an inner gas supply tube extending through the closure plate, an outer tube surrounding the gas supply tube, and having a flange rigid therewith for supporting the outer tube from the closure plate, and screw adjustment means connected to said flange for adjusting the angle of said outer tube relative to said closure plate, the inner tube being fixedly positioned within the outer tube so that its angularity is adjusted concurrently with that of the outer tube; the inner tube having a gas liberating head thereon and the outer tube being substantially larger than the inner tube to permit ready passage of said head, the inner tube extending substantially beyond the outer tube and being positioned with respect thereto by being rigidly secured thereto adjacent to the flange and by having positioning means extending outwardly therefrom at a point remote from said flange to approximately engage the inner surface of the outer tube, a second gas supply tube having a gas liberating head thereon in proximity to the first named head to cooperate in producing a single gas-lift column, the inner tube having substantially rigid characteristics for positioning the head thereon in accurate proximity to the other head.

5. A gas liberating assembly for a liquid-treating tank having a cover provided with an opening, including a closure plate for said opening, an inner gas supply tube extending through the closure plate, an outer tube surrounding the gas supply tube, and having a flange rigid therewith for supporting the outer tube from the closure plate, and means including adjustment screws securing the flange to the closure plate with a predetermined angularity of the outer tube with respect to the closure plate, the inner tube being fixedly positioned within the outer tube to have its angularity with respect to the closure plate determined by that of the outer tube; an updraft tube, the inner tube having a gas liberating head thereon and the outer tube being substantially larger than the inner tube to permit ready passage of said head, the inner tube extending substantially beyond the outer tube and into the updraft tube and being positioned with respect thereto by being rigidly secured to the outer tube adjacent to the flange and by having positioning means extending outwardly therefrom at a point remote from said flange to approximately engage the inner surface of the outer tube, the inner tube having substantially rigid characteristics.

References Cited by the Examiner UNITED STATES PATENTS REUBEN FRIEDMAN, Primary Examiner.

HARRY B. THORNTON, HERBERT L. MARTIN, MAURICE A. BRINDISI, Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,187,897 June 19 5 James Donald Walker It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 18, for "desiged" read designed column 4, lines 42 to 44, strike out "roof, plurality of a means to close said opening including gas-lock tubes" and insert instead roof, means to close said opening including a plurality of gas-lock tubes column 5, line 18, for "Equipmet" read Equipment Signed and sealed this 14th day of June 19660 (SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. A DIGISTER INCLUDING A SUBSTANTIALLY GAS-TIGHT TANK HAVING A ROOF OVERFLOW MEANS FOR RETAINING LIQUOR IN THE TANK TO A PREDETERMINED LEVEL, AN OPENING IN THE ROOF, PLURALITY OF A MEANS TO CLOSE SAID OPENING INCLUDING GASLOCK TUBES SEALED TO THE ROOF AROUND SAID OPENING AND EACH TUBE EXTENDING DOWN INTO THE TANK TO A SUBSTANTIAL DISTANCE BELOW SAID LEVEL TO RETAIN GAS IN THE TANK IN THE SPACE ABOVE THE LIQUOR WHEN SAID TUBE IS OPEN, SCREW MEANS ASSOCIATED WITH EACH GAS-LOCK TUBE ADJACENT THE ROOF FOR ADJUSTING THE ANGULARITY OF THE TUBE IN ANY DIRECTION, AND A GAS SUPPLY PIPE EXTENDING DOWN THROUGH EACH TUBE TO A POINT BELOW THE TUBE, GAS LIBERATING MEANS CARRIED BY EACH PIPE SUBSTANTIALLY BELOW THE TUBE, MEANS NORMALLY SEALING EACH PIPE T ITS SURROUNDING TUBE BUT, SAID PIPE WITH ITS GAS LIBERATING MEANS, BEING REMOVABLE UPWARDLY THROUGH THE TUBE AND THE OPENING, SAID PIPE BEING RIGIDLY POSITIONED IN THE UPPER PART OF SAID GAS-LOCK TUBE AND HAVING MEANS CLOSELY POSITIONED WITH RESPECT TO THE GAS-LOCK TUBE AT A POINT SUBSTANTIALLY LOWER THEREIN THAN THE POINT OF ITS RIGID POSITIONING, AND WITH ITS GAS LIBERATING MEANS BEING OF SUBSTANTIALLY RIGID NATURE THROUGHOUT ITS LENGTH FROM THE POINT OF ITS RIGID POSITIONING DOWN TO ADJACENT THE POINT OF GAS LIBERATION, WHEREBY THE GAS LIBERATING MEANS ARE ACCURATELY POSITIONED WITH RESPECT TO EACH OTHER, THE PLURALITY OF GAS LIBERATING MEANS BEING LOCATED IN PROXIMITY TO ONE ANOTHER TO COOPERATE IN PRODUCING A SINGLE GAS LIFT COLUMN. 